1. Field of the Invention
The present invention relates to a recording apparatus such as an ink jet recording apparatus and a thermal transfer recording apparatus.
2. Description of Related Art
With conventional recording apparatus such as ink jet recording apparatus and thermal transfer recording apparatus, the diameters of a plurality of lots printed on a print medium are varied to provide gradation. For this purpose, the recording head is driven for different time lengths in accordance with print data to control sizes of ink drops ejected from the orifices or amounts of ink thermally transferred to the print medium.
For conventional ink jet recording apparatus, controlling the ink drop size alone cannot provide an adequate size ratio of a minimum dot to a maximum dot to provide a desired gradation. In order to overcome this drawback, acoustic vibration of the ink channel is utilized to eject more than one ink drop successively, which merge into a single large drop before landing on the print medium.
The aforementioned conventional recording apparatus use fixed drive frequencies. If the recording head is driven a longer time for a larger ink drop or driven more than one time for improved gradation, the overall printing time is longer. This leads to a lower printing speed.